The processor speed, in megahertz (MHz), of Intel processors can be approximated by the following function of time $t$ in years since the start of $1995:^{65}$
$$
P(t)=\left\{\begin{array}{ll}
180 t+200 & \text { if } 0 \leq t \leq 5 \\
3,000 t-13,900 & \text { if } 5<t \leq 12
\end{array}\right.
$$
a. Is $P$ a continuous function of $t$ ? Why? HINT [See Example 4 of Section 10.3.]
b. Is $P$ a differentiable function of $t ?$ Compute $\lim _{t \rightarrow 5^{-}} P^{\prime}(t)$ and $\lim _{t \rightarrow 5^{+}} P^{\prime}(t)$ and interpret the results. HINT [See Before we go on... after Example 5.]